Electromechanical refueling control system

ABSTRACT

A method for actuating an onboard refueling vapor recovery (ORVR) valve to selectively enable passage of fuel vapor from a fuel tank to a collection canister for the fuel vapor. The method includes determining whether a filling event is occurring and determining a fuel level within the fuel tank. The ORVR valve is selectively opened and closed in connection with whether a fueling event occurs and whether the fuel tank is full.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to vapor recovery systems for vehiclesand, more particularly, to an onboard refueling vapor recovery systemusing an electronic control valve and a method for operating theelectronic control valve.

2. Discussion

Increasingly stringent environmental standards have resulted in thepassage of regulations which necessitate a significant reduction in fuelvapors escaping from a vehicle fuel tank during refueling. Theseregulations generally strive to essentially eliminate fuel vaporescaping to the atmosphere during refueling. The resultant emissioncontrol systems are referred to as onboard refueling vapor recovery(ORVR) systems. In an ORVR system, the filler neck of the fuel system isdesigned to a diameter to create a liquid seal in the filler neck toprevent vapors from escaping from the fuel tank through the filler neck.During refueling, the fuel volume within the tank increases, therebyreducing the available space for fuel vapors. The pressure created byfilling the tank causes the fuel vapors to exit through an exhaust portto a fuel vapor canister. The fuel vapor canister typically includes acharcoal element to capture hydrocarbons while releasing filtered vaporsinto the atmosphere.

In a typical ORVR system, a control valve is placed in the vaportransmission path between the fuel tank and the canister. The primarypurpose of the control valve is to enable the transmission of vaporwhile preventing the transmission of liquid fuel to the collectioncanister. If liquid fuel reaches the canister, a situation referred toas carryover, fuel can collect within the canister. Because the canistermay later be purged to provide fuel to the vehicle via the intakemanifold, excessive fuel carryover may cause liquid fuel to exit thefuel system or interfere with engine operation.

Existing ORVR control valves are mechanical valves which are normallyopen, providing a vapor path between the fuel tank and the canister.However, these normally open valves must be adaptable to close off thevapor path between the fuel tank and the canister during conditions suchas vibration, slosh, and vehicle tilting which might otherwise result ina carryover condition. Typical valves include a buoyant member with abias toward an open position. The valve is responsive to slosh,vibration, and tilting conditions to close the vapor passage. However,such valves are often slow to respond and include many moving partswhich eventually deteriorate, thereby adversely affecting operation ofthe refueling valve.

Thus, it is an object of the present invention to provide an onboardrefueling vapor recovery system having an electronic control valve toselectively enable the passage of fuel vapor from the fuel tank to thecanister during predetermined conditions.

It is a further object of the present invention to provide an onboardrefueling vapor recovery system having an electronic control valve whichis generally closed to prevent liquid fuel from traveling to thecanister, except during refueling when the electronic control valve isopened.

It is yet a further object of the present invention to provide anonboard refueling vapor recovery system having an electronic controlvalve and a method for controlling the electronic control valve whichenables vapor to pass from the fuel tank to the canister only duringpredetermined conditions.

It is yet a further object of the present invention to provide a methodfor controlling an onboard refueling vapor recovery system having anelectronic control valve, where the method prevents liquid fuel fromtraveling to the canister.

SUMMARY OF THE INVENTION

This invention is directed to an onboard refueling vapor recovery (ORVR)system. The ORVR system includes a fuel tank and a vapor recoverycanister. A vapor passage connects the fuel tank and the vapor recoverycanister. An electrically operated ORVR valve is disposed in the vaporpassage. The ORVR valve enables vapor to pass between the fuel tank andcanister when in an open position and prevents liquid and vapor frompassing between the fuel tank and canister when in a closed position. Afill sensor detects when fuel is being introduced into the fuel tank,defined as a fueling event. The fill sensor generates a fill signal toindicate the fueling event. The ORVR valve is responsive to the fillsignal and opens during a fueling event.

This invention is also directed to an onboard refueling vapor recovery(ORVR) valve. The valve includes an inlet port in communication with aninterior of a fuel tank and an outlet port in communication with acanister. A passage connects the inlet port and the outlet port. A valveis disposed in the passage between the inlet and the outlet ports toselectively open and close the passage. A solenoid opens and closes thevalve in accordance with an electrical signal, where the electricalsignal is generated in accordance with introduction of fuel into thefuel tank. The valve is opened during the introduction of fuel into thefuel tank provided that the tank is not full.

This invention is also directed to a method for recovering vapor duringan onboard refueling operation in a vehicle. The method includesproviding a flow path between a fuel tank and a collection canister. Themethod also includes providing a fueling event sensor for detecting atleast one of the introduction of fuel into the fuel tank or theintroduction of a filler nozzle into a filler neck of the fuel tank,defined as a fueling event. The method further includes providing anORVR valve in the flow path and actuating the ORVR valve in accordancewith the output of the fueling event sensor to selectively open andclose the flow path.

These and other advantages and features of the present invention willbecome readily apparent from the following detailed description, claimsand drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, which form an integral part of the specification, are tobe read in conjunction therewith, and like reference numerals areemployed to designate identical components in the various views:

FIG. 1 is a block diagram of an onboard refueling vapor recovery (ORVR)system arranged in accordance with the principles of the presentinvention;

FIG. 2 is a cross-sectional view of an electronic ORVR control valve inthe system of FIG. 1;

FIG. 3 is a bottom view of the ORVR control valve of FIG. 2;

FIG. 4 is a perspective view of the top cover of the ORVR control valveof FIGS. 2 and 3;

FIG. 5 is a cross-sectional view of a portion of a fuel tank including abuoyant member for signaling that the fuel tank is full;

FIG. 6 is a first embodiment for a filler neck switch to indicate that afill nozzle has been inserted into the filler neck;

FIG. 7 is a second embodiment of a filler neck switch to indicate that afill nozzle has been inserted into the filler neck;

FIG. 8 is a third embodiment of a filler neck switch operable to sensethe flow of fuel into the filler neck;

FIG. 9 is a block diagram of a second embodiment of an ORVR system; and

FIG. 10 is a flow chart of a method of operating an ORVR control valve.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the figures generally and FIG. 1 in particular, an onboardrefueling vapor recovery (ORVR) system 10 is shown. ORVR system 10includes a fuel tank 12 which stores a volume of fuel 14. A vapor space16 forms above fuel 14 and contains evaporated vapors from fuel 14. Afiller tube 18 provides access to fuel tank 12 so that fuel 14 may beprovided into fuel tank 12. Filler tube 18 includes a filler neck 20which defines a narrowed section which interacts with a filler nozzleshown in FIGS. 6 and 8 to provide a liquid seal during refueling. Acheck valve 22 located downstream of filler neck 20 contains vapor andfuel within tank 12 and also prevents spitback of fuel during refueling.

A vapor passage 24 enables vapor in vapor space 16 to pass from fueltank 12 to a canister 26. Canister 26 is typically filled with charcoal28 to enable collection of hydrocarbons in the fuel vapor. The vaporpasses through charcoal 28, where the hydrocarbons are removed, andescapes canister 26 through canister vent 30. During vehicle operation,hydrocarbons may be removed from charcoal 28 in canister 26 by providinga vacuum from the engine 34 through vacuum path 36. A canister purgevalve 32 regulates the vapor flow rate through vacuum path 36.

Of particular relevance to this invention, vapor passage 24 includes anelectronically controlled ORVR valve 38. ORVR valve 38 operates toselectively open and close the flow path between fuel tank 12 andcanister 26, thereby enabling selective flow of vapor from fuel tank 12to canister 26. Preferably, such flow occurs only during refueling, orin accordance with other predetermined design considerations. ORVR valve38 includes a valve portion 40 which opens and closes vapor passage 24.ORVR valve 38 also includes an electromechanical solenoid 42, 42receives control signals from electronic control unit 44 on signal line46. Solenoid 42 operates valve 40 in accordance with the control signalsgenerated by electronic control unit 44.

Electronic control unit 44 receives an input signal from a fuel fillerswitch 48 on signal line 50. Fuel filler switch 48 preferably emits asignal indicating that a filler nozzle of a fuel pump or can has beeninserted into filler neck 20, thereby signaling a refueling event.Electronic control unit 44 also receives at least a first signal emittedby fill level sensor 52 on signal line 56. Fill level sensor 52preferably emits a signal when the level of fuel 14 is above apredetermined threshold 64 in fuel tank 12, generally indicating thatfuel tank 12 is full. Similarly, a level sender 54 outputs a signal onsignal line 56 to electronic control unit 44. Level sender 54 preferablyemits a variable output signal which varies in accordance with the levelof fuel 14 in fuel tank 12. It should be noted that level sensor 52 andlevel sender 54 may be used individually or cooperatively, depending onspecific design considerations.

ORVR system 10 also includes a rollover valve 58 mounted in an openingin fuel tank 12. Rollover valve 58 provides a containment function in arollover situation and also provides a vapor flow path during arefueling event and after ORVR valve 38 has closed vapor passage 24. Arecirculation line 60 interconnects vapor passage 24 to filler tube 18at an upstream side of filler neck 20. A restrictor 62 limits vapor flowthrough restrictor line 60.

ORVR valve 38 will be described with respect to FIG. 2-4. As shown inFIG. 2, valve 40 of ORVR valve 38 is shown in a closed position. ORVRvalve 38 has an input port 70 located at a bottom portion of ORVR valveand 38 an output port 72 located in a top portion of ORVR valve 38. Abypass port 74 is formed to communicate with output port 72 and connectsto bypass line 60. Output port 72 and bypass port 74 are formed in a topcover 76 which is formed of HDPE material. Top cover 76 is preferablymounted on top of fuel tank 12 so that solenoid 42 and input port 70descend into tank 12. Top cover 76 includes an electrical connector 78to enable power to be supplied to solenoid. Top cover 76 may alsoinclude a housing 80 formed to receive a control circuit, such aselectronic control unit 44, so that ORVR valve 38 forms a generallyself-contained module. Top cover 76 forms an annular valve seat 82 ofvalve 40. An elastomer seal 84 is selectively positioned to contact seat82 to close vapor passage 24 or, alternatively, is displaced away fromseat 82 to open vapor passage 24.

Selective opening and closing of valve 40 occurs through activation anddeactivation of solenoid 42. Solenoid 42 connects to top cover 76 via anouter shell 90 which includes radial tabs 92 which molded or otherwiseconnected to top cover 76. Retaining outer shell 90 includes inward tabs94 which engage an inner shell 96. Inner shell 96 includes inward tabs98. Inward tabs 98 of inner shell 96 retain a disk spring 100 at lowerportion of solenoid 42.

Solenoid 42 includes a bobbin 106 placed concentrically with andretained within inner shell 96. A coil 108 is wound upon bobbin 106. Astator 110 is inserted within a central bore 112 of bobbin 106. A shaftmember 114 connects at its upper end to piston 86 and is guided by acentral bore 118 in stator 110 during axial movement of piston 86 andattached shaft 114. Piston 86 is press fit within armature 116 so thatmovement of armature 116 causes a corresponding movement of piston 86and elastomer seal 84, thereby opening and closing valve 40.Energization of coil 108 generates a magnetic field which exerts agenerally downward force upon armature 116. Upon deenergization ofsolenoid 42, the generally downward force upon armature 116 dissipates,thereby enabling disk spring 100 to exert a generally upward force uponshaft member 114 and rigidly attached piston 86, thereby closing valve40. As shown in FIG. 4, electrical connections 122 may be routed toelectrical coil 108 from electrical control unit housing 80 in order toselectively actuate coil 108.

As best seen in FIGS. 3 and 4, top cover 76 may be formed with anoptional integral fill level sensor 120. Fill level sensor 120 ispreferably a thermister liquid level sensor which generates a variableresistance in accordance with the sensed temperature. In operation,contact with fuel effects a temperature change up thermister 120. Thetemperature change varies the resistance of the thermister liquid levelsensor, generally indicating that the fuel tank is full. Fill levelsensor preferably is positioned within fuel tank 12 in order to provideoptimum fill capacity. For example, with respect to FIG. 1, level sensor52 may be embodied as fill level sensor 120 and may be displaced from adescending member as shown in FIG. 1.

FIG. 5 depicts a portion of an ORVR system 130 having an ORVR valve 38placed in a vapor passage 24 which interconnects fuel tank 12 to acanister, not shown in FIG. 5. ORVR system 130 of FIG. 5 includes amechanical level sensor 132 formed in fuel tank 12. Level sensor 132includes a vapor passage 134 which descends from an upper surface 136 oftank 12. Level sensor 132 also includes a float portion 138 attached toa lower section of passage 134. Float portion 138 includes a buoyantmember 140. Buoyant member 140 has a density that enables it to floatatop fuel. Preferably, a passage 134 is sealed to top cover 76, and topcover 76 is sealed to fuel tank 12.

In operation, level sensor 132 determines the fill height of tank 12when buoyant member 140 rises to close off passage 134. The fill heightdetermined by level sensor 132 is determined in accordance with thelength L of passage 134. When the fuel level causes buoyant member 140to seat against the bottom surface 142 of passage 134, level sensor 132prevents liquid fuel and fuel vapor from entering passage 134 andflowing to the canister. During a fill operation, closing passage 134causes a resultant back-pressure to deactivate the typical fill nozzle.When the fuel height drops so that passage 134 is open, level sensor 132enables vapor to flow into passage 134. When level sensor 132 is used incooperation with ORVR valve 38, passage of vapor and fluid can occuronly during a refueling operation as ORVR valve 38 is otherwise closed.Level sensor 132 also operates in cooperation with ORVR valve 38 toprevent sloshed fuel from flowing to the canister. Sloshed fuelcorrespondingly causes buoyant member 140 to rise against bottom surface142 of passage 134, thereby preventing the sloshed fuel from enteringpassage 134.

In order to properly operate ORVR system 10 of FIG. 1, fuel fill switch48 generates a signal output on signal line 50 to electronic controlunit 44 to indicate that fuel may be introduced into fuel tank 12. Thesignal generated on signal line 50 may result from the introduction of afiller nozzle, such as from a fuel pump, to filler tube 18 and fillerneck 20. Alternatively, liquid sensors may be used to detect theintroduction of fuel into filler tube 18 and filler neck 20.

FIG. 6 depicts one embodiment of a mechanical switch system 150 fordetecting the presence of a filler nozzle 152. Filler nozzle 152typically is of a length to pass into filler tube 18 and filler neck 20.As shown in FIG. 6, a switch 154 includes a switch lever 156 whichrotates about a pivot axis 158. Switch lever 156 includes a flapper door160 and a contact arm 162. Switch lever 156 is generally biased, such asby a spring or other biasing means, so that flapper door 160 generallydiametrically crosses filler neck 20. When filler nozzle 152 is insertedinto filler neck 20, filler nozzle 152 displaces flapper door 160,causing rotational movement of switch lever 156. The rotational movementcauses contact arm 162 to displace pin 164. Displacing pin 164 activateselectrical switch 166.

Electrical switch 166 assumes at least two positions. In a firstposition, with flapper door 160 biased across filler neck 20, because nofiller nozzle 152 is inserted into filler neck 20, electrical switch 166disables continuity between electrical conductors 168. When a fillernozzle 152 is inserted into filler neck 20, thereby rotating switchlever 156 and displacing pin 164 toward electrical switch 166,electrical switch 166 enables continuity between electrical conductors168. Enabling continuity between conductors 168 provides a signal toelectronic control unit 44 of FIG. 1 that a fueling event is occurring.

FIG. 7 depicts an alternative nozzle detection system 170 utilizing areed switch 172. The filler tube 18 includes a nozzle guide 174 whichmay be placed within filler tube 18. Nozzle guide 174 includes walls 176which guide a filler nozzle, not shown in FIG. 7, downstream towardfiller neck 20. Nozzle guide 174 includes a flapper door 178 which isgenerally biased so as to cover opening 182 of nozzle guide 174. Flapperdoor 178 includes a magnet 184 attached to a tank side surface offlapper door 178. When a nozzle is inserted into nozzle guide 174 so asto rotate flapper door 178 to an open position, magnet 184 actuates reedswitch 172. Activation of reed switch 172 provides a conductive pathbetween a conductor 186 and a conductor 188. When reed switch 172 isclosed, the conductive path provides a signal to electrical control unit44 of FIG. 1 indicating the occurrence of a fueling vent.

Rather than sensing insertion of a filler nozzle into the filler neck,other fueling detection systems can be used, including a liquiddetection system. FIG. 8 depicts one embodiment of a liquid detectionsystem 190. A thermister is placed within filler neck 20. A pair ofconductors 194, 196 provides a current path through thermister 192. Whenfuel flows through filler neck 20, the current passing throughthermister 192 changes due to variation in the resistance of thermister192 resulting from temperature variation due to fuel flow. The change incurrent through thermister 192 maybe be monitored by electronic controlunit 44 of FIG. 1 in order to detect introduction of fuel into fuel tank12.

FIG. 9 depicts a second embodiment of an ORVR system 200. The ORVRsystem 200 of FIG. 9 includes several sensors which generate signalsinput to an electronic control unit 220. The sensors include a fill doorsensor 202 which generates a signal when the fuel fill door is open. Afill pipe sensor 204 and a fill neck check valve sensor 206 emit signalsto electronic control unit upon detecting a filler nozle inserted to thefill pipe. Alternatively, one or both of these sensors may be responsiveto detection of fluid flowing through a fill pipe and emit a signal toelectronic control unit 220 accordingly. A level sensor 208 generates asignal that varies in accordance with the fuel level within the tank.Level sensor 208 preferably emits a variable signal to electroniccontrol unit 220 which varies in accordance with the level of fuel inthe tank. A mechanical valve 210 emits an electrical signal toelectronic control unit 220. Mechanical valve 210 emits a signal whenfuel rises above a predetermined level, thereby tripping a mechanicalelement. A fill level sensor 212 operates similarly to level sensor 208,except fill level sensor 212 generates a signal when the fuel reaches apredetermined level. The signal generated by fill level sensor 212preferably is binary signal which simply indicates that the fuel exceedsa predetermined level. Ignition sensor 214 generates an output signal toelectronic control unit 220 in accordance with the state of theignition. For example, if the ignition is activated, ignition sensor 214outputs an appropriate electronic signal. Gearshift sensor 216 generatesa variable signal to electronic control unit in accordance with thestate of the vehicle gear shift. For example, gearshift sensor 216 maygenerate signals corresponding to park, neutral, the various forwardgears, and reverse. Speed sensor 218 also generates a variable signal toelectronic control unit 220, where the signal output by speed sensor 218varies in accordance with the vehicle speed.

Sensors 202-218 generate their respective signals to electronic controlunit 220. Electronic control unit 220 processes the signals inaccordance with predetermined criteria and generates a signal to ORVRvalve 222 to actuate ORVR valve 222 in accordance with the predeterminedcriteria. When actuated, ORVR valve 222 provides a vapor passage pathbetween fuel tank 224 and canister 226. When deactuated, ORVR valve 222closes the path between fuel tank 224 and canister 226.

FIG. 10 depicts a block diagram 230 for a method of operating the ORVRvalves described above. The method commences at start block 232. Controlproceeds from start block 232 to decision block 234. At decision block234, a test is conducted to determine whether a filling event isoccurring. A filling event may generally be described as theintroduction of a filler nozzle or fuel into the fuel tank. A fillingevent may be detected by detecting a fuel pump fill nozzle in the fillertube 18 or filler neck 20 or may be detected by sensing fuel in fillertube 18 or filler neck 20. If no filling event is detected, controlproceeds to close ORVR valve block 236. At close ORVR valve block 236, asignal is initiated to close the ORVR valve, thereby closing the vaporpassage between the fuel tank and the canister. Following closure of theORVR valve, control proceeds to end block 238.

Returning to detect filling event block 234, if a filling event isdetected, control proceeds to decision block 240. At decision block 240,a test is conducted to determine if the tank liquid level sensor detectsfuel at a predetermined level. For example, such a sensor may be a filllevel sensor which simply determines if the level of fuel in the tankexceeds a predetermined level. Alternatively, a circuit may process avariable signal from a sending unit, such as may be used for a fuelgauge, to determine the level of fuel in the tank. If the determinedlevel of fuel in the tank exceeds a predetermined threshold, the tank isconsidered full. At decision block 240 if the tank is considered full,control proceeds to close ORVR valve block 236 and then to end block238. If the tank is determined not to be full, control proceeds to openORVR valve block 242. At open ORVR block 242, an ORVR valve signal issent to the ORVR valve to close the solenoid, thereby closing thepassage between the fuel tank and the canister. Control then proceed toend block 238.

The foregoing system offers several benefits over existing systems. Inparticular, the ORVR systems described herein provide negligible fuelcarryover through the control valve during any static or dynamic fuelmanagement event. Further, the ORVR systems described herein offerimproved fill quality by providing the ability to reach desired factoryfill rates because the system is less susceptible to blowshut andcorking. The ORVR system further offers consistent fill levelsindependent of the fill rate and fuel density.

While specific embodiments have been shown and described in detail toillustrate the principles of the present invention, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles. For example, one skilled in the art willreadily recognize from such discussion and from the accompanyingdrawings and claims that various changes, modifications and variationscan be made therein without departing from the spirit and scope of theinvention as described in the following claims.

What is claimed is:
 1. A method for recovering vapor during an onboardrefueling operation in a vehicle comprising the steps of: providing aflow path between a fuel tank and a collection canister; providing afueling event sensor for detecting at least one of the introduction offuel into the fuel tank and the introduction of a filler nozzle into afiller neck of the fuel tank, defined as a fueling event; providing anORVR solenoid valve in the flow path; actuating the ORVR valve inaccordance with the output of the fueling event sensor to selectivelyopen and close the flow path; providing a level sensor for detecting apredetermined fuel level in the fuel tank; and actuating the ORVR valveto selectively open and close the flow path in accordance with anelectrical signal output of the fueling event sensor and the levelsensor.
 2. The method of claim 1 further comprising the step of openingthe ORVR solenoid if the output of the fueling event sensor indicates afueling event is occurring and if the level sensor indicates a fuellevel below the predetermined fuel level.
 3. The method of claim 1further comprising the step of closing the ORVR solenoid if the outputof the fueling event sensor indicates a fueling event is occurring andif the level sensor indicates a fuel level at the predetermined fuellevel.
 4. The method of claim 1 further comprising the step of closingthe ORVR solenoid if the output of the fueling event sensor indicatesthat no fueling event is occurring.
 5. A method for recovering vaporduring an onboard refueling operation in a vehicle comprising the stepsof: providing a flow path between a fuel tank and a collection canister;providing a fueling event sensor for detecting at least one of theintroduction of fuel into the fuel tank and the introduction of a fillernozzle into a filler neck of the fuel tank, defined as a fueling event,the fueling event sensor generating a fueling event signal; providing anORVR solenoid valve in the flow path; selectively actuating the ORVRvalve in accordance with the output of the fueling event sensor in orderto selectively open and close the flow path; providing a control circuitto evaluate the fueling event signal, the control circuit generating anORVR signal to control operation of the ORVR solenoid; and providing alevel sensor for detecting a predetermined fuel level in the fuel tank,the level sensor generating a fuel level signal, wherein the controlcircuit evaluates the fueling event signal and the fuel level signal,the control circuit generating the ORVR signal in accordance with theevent and fuel level signals to control operation of the solenoid. 6.The method of claim 5 further comprising the step of opening the ORVRsolenoid if the output of the fueling event sensor indicates a fuelingevent is occurring and if the level sensor indicates a fuel level belowthe predetermined fuel level.
 7. The method of claim 5 furthercomprising the step of closing the ORVR solenoid if the output of thefueling event sensor indicates a fueling event is occurring and if thelevel sensor indicates a fuel level at the predetermined fuel level. 8.The method of claim 5 further comprising the step of closing the ORVRsolenoid if the output of the fueling event sensor indicates that nofueling event is occurring.
 9. A method for recovering vapor during anonboard refueling operation in a vehicle comprising the steps of:providing a flow path between a fuel tank having a filler neck and acollection canister; providing a fueling event sensor for detecting afueling event and sending an electrical signal to an ORVR solenoid;providing a level sensor for detecting a predetermined fuel level in thefuel tank; providing an ORVR solenoid in the flow path for selectivelyopening and closing the flow path; and selectively opening and closingthe flow path in accordance with the output of the fueling event sensorand the level sensor; and opening the ORVR solenoid in response to anelectrical signal output of the fueling event sensor indicating afueling event is occurring and if the level sensor indicates a fuellevel below the predetermined fuel level.
 10. The method of claim 9further comprising the step of closing the ORVR solenoid if the outputof the fueling event sensor indicates a fueling event is occurring andif the level sensor indicates a fuel level at the predetermined fuellevel.
 11. The method of claim 10 further comprising the step of closingthe ORVR solenoid if the output of the fueling event sensor indicatesthat no fueling event is occurring.